CiRCLE Studio Ltd is an independent UK games developer that was founded in 2003 by Jeremy Heath-Smith and Adrian Smith. The Smith brothers share more than 39 years of collective experience in the gaming industry. They are the original founders of Core Design and responsible for numerous software hits, including the Tomb Raider series and one of the world's most successful video game icons, Lara Croft. The development studio is largely comprised of former Core Design staff.

In Without Warning, a radical terrorist group has targeted and seized the Peterson-Daniels Chemical Facility, a vulnerable location that jeopardizes millions of people from the devastating ecological hazard it imposes if destroyed. Pleas are useless and any direct military assault would be too great a risk. As terrified hostages fear for their lives, their only hope lies with a covert operations team, whose goal is to infiltrate the plant and eliminate the merciless enemy.

The harrowing events unfold over a 12 hour period, featuring a unique gameplay dynamic which enables the six central characters to experience events across the same timeline but from their own distinct viewpoints. The player controls each character individually, with the focus automatically shifting to a new character at key moments which are unfolded through cut scenes. By switching between the characters, their individual tales are woven together to create an overall picture of the events that happened during the crisis. The player will also retrospectively view events through the eyes of another character and is therefore not only a participant in the events, but a spectator as well. Furthermore, actions performed as one character affect the progress of others and players must successfully utilize the strengths of each in order to advance.

Without Warning includes the following features:

• Play as six different characters and experience the game from each of their perspectives:
• Three members of the covert operations team :
  • Kyle Rivers – the leader of the squad with an experienced combat background
  • Jack Hooper – the youngest and most inexperienced member of the team for whom this is the first combat mission
  • Ed Reagan – the squad's bomb disposal specialist who is also formidable in close combat situations
• Three civilians with distinct agendas and views on the events:
  • Tanya Shaw – a terrified secretary whose only desire is to escape safely
  • Dave Wilson – a security guard who was overlooked by the terrorists; his fierce determination drives him as he fights to rescue his co-workers
  • Ben Harrison – a news cameraman who is grounded when his helicopter is shot down by the terrorists; his quest is to obtain breaking news coverage, however dangerous it may be
• Diverse gameplay – exploration, puzzle-solving, dynamic environmental interaction, and a variety of sub missions including bomb diffusion and hostage rescue
• Objective based gameplay progression
• Sophisticated graphics – realistic and highly interactive environments, advanced character animations with well defined emotions, and gripping cut scenes that link the storylines together
• Progressive tutorial – instructs players on how to utilize the vast arsenal of weaponry and equipment
• Fully controllable camera – moves fluidly around characters to rapidly survey surroundings and enable them to change tactics accordingly